There are really two novels here -- one a gritty, futuristic picaresque straight out of the Bruce Sterling tradition (part "Schismatrix", part "Taklamakan"), and the other a down-to-Earth tale of people and ideology that owes more to Iain without-the-M Banks (think "Espedair Street" with a bit of "The Business").
The former is stronger, with some beautifully evocative description and brilliant, snappy dialogue, as well as a tongue-in-cheek yet sincere take on the anarcho-capitalism that seems to be the in thing in SF these days. The colony world of New Mars is one of the most real places I've found in SF for a while; its inhabitants are not just three-dimensional but fun to hang out with.
The latter is at its best, story-wise, when its characters are excitable 1970s undergraduates; as it follows them into the next century they seem to fade against the brightly painted background of "Snow Crash"- style nation-dismantling and Prague-style reactionary backlash. It picks up again at the end of the next century, as it jumps closer to the inevitable connection with the first storyline; there are some throwaway ideas in there as brilliant, and as surprising, as you'd find in, say, Greg Egan.
The ending isn't quite satisfying, but it's worth it for the ride -- and besides, you can always go on and read "The Cassini Division".
It's not MacLeod's best work, but it's better than the best work of a lot of authors out there. And having read some of his other stuff, I know it gets better from here.